Chapter 3 - Enzymes 2024

Unit 3 AOS1 MW Biology: Chapter Overview

  • Chapter 3: Enzymes

    • 3A: Introducing Enzymes

    • 3B: Factors Affecting Enzymes

Study Design

  • Proteins

    • Diverse group forming an organism's proteome

    • Includes enzymes as key catalysts in biochemical pathways

  • Factors Impacting Enzyme Function:

    • Temperature

    • pH

    • Concentration levels

    • Competitive and non-competitive enzyme inhibitors

  • Role of Enzymes and Coenzymes

    • Facilitate steps in photosynthesis and cellular respiration

3A: Introducing Enzymes

  • Definition of Enzymes

    • Organic catalysts that speed up biochemical reactions

    • Bind to substrates (reactants undergoing reaction)

  • Active Site

    • Each enzyme contains a specific active site complementary to the substrate's shape

    • Forms an enzyme-substrate complex upon binding, which leads to a conformational change.

  • Reaction Process

    • Substrate undergoes a chemical transformation to yield products

Specific Examples

  • Enzyme Example: Maltase

    • Substrate: Maltose

    • Products: Glucose

  • Enzyme-Substrate Interaction

    • An enzyme's active site allows binding of specific substrates, facilitating unique reactions

Characteristics of Enzymes

  • Reusable

    • Enzymes are not consumed in reactions and can catalyze multiple reactions

  • Specificity

    • Each enzyme typically acts upon one specific substrate

  • Catalysis

    • Enzymes lower activation energy required for reactions

Enzyme Functioning

  • Conformational Change

    • Upon substrate binding:

      • Enzyme changes shape to enhance fit with substrate

      • Results in successful product formation

Activation Energy

  • Definition:

    • Minimum energy required for a reaction

  • Effect of Enzymes:

    • Enzymes lower the activation energy, facilitating faster reactions

Types of Reactions

  • Catabolic Reactions

    • Larger molecules break down into smaller ones, releasing energy

  • Anabolic Reactions

    • Smaller molecules combine to form larger ones, storing energy

3B: Factors that Affect Enzymes

  • Temperature Impact on Enzyme Activity

    • Too Cold: Reduced activity due to slower molecular movement

    • Optimal Temperature: Increased kinetic energy leading to more substrate interactions

    • Too Hot: Risk of denaturation, where enzymes lose shape and can no longer function

  • pH Influence

    • Variations can lead to enzyme denaturation

    • Optimal pH varies by enzyme type (e.g., pepsin in stomach has pH of ~1.5-2)

  • Concentration Effects

    • Substrate Concentration: Increased concentration elevates reaction rates until saturation is reached

    • Enzyme Concentration: Higher enzyme concentrations lead to faster reactions until enzyme saturation occurs

  • Inhibition Types

    • Competitive Inhibition: Inhibitor blocks active site, preventing substrate binding

    • Non-competitive Inhibition: Inhibitor binds elsewhere, altering active site shape

Coenzymes

  • Assistance in Reactions:

    • Cofactors are needed for some enzyme reactions; coenzymes are organic cofactors

    • Coenzymes assist by donating energy/molecules that cycle through reactions

Example of a Coenzyme: ATP

  • Function: Main energy carrier in cells

  • Process:

    • Releases energy by losing a phosphate group (ATP to ADP)

    • Can return to ATP through rephosphorylation

Exam Strategies

  • Read questions carefully

  • Highlight key information in prompts

  • Assess question requirements based on mark allocation

  • Ensure response length meets expected answers, based on allocated marks